1) Field of the Invention
The present invention relates to the electrical connection of susceptors and, more particularly, to a system for releasably connecting susceptors and controlling the temperature of the susceptors, such as in an apparatus for heating and processing workpieces.
2) Description of Related Art
Induction heated susceptors are used for heating during various operations, such as in an apparatus for forming, joining, or otherwise processing composite or metallic members. For example, U.S. Pat. No. 6,180,932, titled “Brazing Honeycomb Panels with Controlled Net Tooling Pressure,” describes a method of induction brazing honeycomb panels in a workcell using susceptor sheets that are heated to a brazing temperature. U.S. Pat. No. 5,530,227, titled “Method and Apparatus for Consolidating Organic Matrix Composites Using Induction Heating,” and U.S. Pat. No. 5,420,400, titled “Combined Inductive Heating Cycle for Sequential Forming the Brazing,” describe apparatuses and methods for forming workpieces of organic matrices and metals in which the workpiece is also heated by inducing a current in a susceptor. Generally, an electrical current can be induced in such a susceptor, and the current heats the susceptor until the susceptor reaches a Curie temperature. When a portion of the susceptor reaches the Curie temperature, that portion becomes paramagnetic and the current flows around that portion of the susceptor. Thus, the susceptor can heat the workpiece uniformly to a target temperature as required for forming, bonding, or otherwise processing the workpiece.
The susceptors can be provided as sheets that envelope the workpiece, i.e., first and second susceptor sheets can be disposed on opposite sides of the workpiece. The susceptor sheets are connected at a periphery so that the current induced in the susceptors can flow in a path through both of the susceptors and around the workpiece. For example, the peripheries of the susceptors can be welded together to achieve a satisfactory electrical contact therebetween. However, welding of the susceptor sheets generally increases the time and cost of the operation. Further, the welding or subsequent destruction of the weld joints (e.g., to remove the workpiece from between the susceptors) can damage the susceptors and prevent their re-use. Alternatively, as described in U.S. Pat. No. 6,180,932, the edges of the susceptors can be joined using crimps, gaskets, or a compression edge seal. Such non-weld joints can be formed relatively quickly and can be easily released so that the susceptor can be re-used. However, the contacting portions of the susceptors can oxidize or otherwise degrade during operation of the apparatus, thereby affecting the electrical contact resistance between the susceptors. In some cases, it may be necessary to regularly clean the contacting portions of the susceptors or replace the susceptors to ensure satisfactory electrical contact.
Thus, there exists a need for an improved susceptor connection system and an associated processing apparatus and method. The susceptor connection system should be easily connected and released and should reduce the occurrence of oxidation or other degradation of the contact portions of the susceptors. The connection system should be compatible with susceptors for different processing operations.